In last year’s budget talks, Congress set up the prospect of $500 billion in automatic cuts in military spending to help pressure political leaders to reach a broader deficit-reduction deal.

The cuts, which would start with $50 billion next year, would be disruptive. But military analysts say they could be phased in more gradually than originally thought, eliminating the need for furloughs or layoffs Jan. 2.

As a result, White House officials and House Republicans believe that they can limit the fallout at the Pentagon if they miss that deadline and reach a larger budget deal sometime next year.

“It’s not like a government shutdown, where things close and the lights go out,” said Todd Harrison, an analyst at the Center for Strategic and Budgetary Assessments, a research group in Washington. “It looks more like a glide slope than going down a cliff.”

Defense Secretary Leon E. Panetta who has said that the automatic cuts would be catastrophic, also toned down his remarks in a memorandum to Pentagon employees Thursday.

“These cuts, while significant and harmful to our collective mission as an agency, would not necessarily require immediate reductions in spending,” he wrote. But, he added: “Should we have to operate under reduced funding levels for an extended period of time, we may have to consider furloughs or other actions in the future.”

Under the law that created the process, known as sequestration, uniformed members of the military would be exempt from furloughs or pay reductions, and war spending would be protected.

But a significant number of the Pentagon’s civilian employees could be furloughed or laid off, as could some of the contractors who build weapons systems and provide services to the military.

The plan was created to cut spending automatically if the White House and Congress could not agree on how to meet caps on discretionary spending. Panetta has said sequestration would act like a meat ax, chopping about 10 percent off most Pentagon programs next year. If the plan is not altered, the cuts would add up to $500 billion over 10 years.

The House voted 215-209 on Thursday night to cancel the military cuts. The narrow margin in the House, which has 241 Republicans, suggested that “the floor is getting soft under defense spending” in general, said Gordon Adams, who helped oversee military budgets in the Clinton White House.

Harrison, the budget center analyst, said that if the automatic cuts were to start Jan. 2, they would unfold in several stages. The fiscal year started Oct. 1, so the Pentagon would have three quarters in which to shave about $50 billion from its base budget of more than $525 billion.

“There would be no immediate layoffs,” he said.

And weapons programs that had already been financed would keep going.

By next spring, the Pentagon would probably have to furlough or lay off civilian employees, and “things could get messy,” he said. It would also have to slow awards of new contracts, and it would have fewer employees to oversee contractors, causing more delays.